Thermal imaging systems have found an increasing number of applications in the military and industry. Thermal gradients in scenes containing strategic military targets are transduced to visible images in real time by means of infrared scanning systems. The improvement of these military infrared systems has resulted in spinoffs into the industrial area. Infrared scanners are used, for example, in railroad environments for hot box detection in wheel bearings as the train passes. The uses in the medical field have only touched the surface of such applications as the detection and localization of cancer cells, sinus conditions and skin difficulties. In forestry thermal imagery can detect diseased trees and sources of forest fires in dense smoke. The applications in factory type environments requiring remote temperature measurements are limited only by expense. The IR microscope has many uses in the research community for location of hot areas in microcircuits and similar small systems.
One of the more potentially promising systems in the low cost infrared scanning community is the pyroelectric vidicon. This device is a simply modified vidicon wherein a pyroelectric target material is substituted for the normal target, and the voltages are modified slightly to include an erasure scheme due to target memory. Operation involves the far infrared scene being focused onto the target material. The pyroelectric effect in the target material reorients the polarization vectors proportional to the rate of change of the two dimensional energy density from the thermal scene. This dynamic detection characteristic means the pyroelectric vidicon can only detect changing thermal scenes, i.e., the device operates in an AC mode. In nonscanned systems, it would detect only moving targets. In many applications, it is desirable to image a stationary scene. This requires some type of scanning system which moves the picture elements (PIXELS) of the thermal scene over a finite portion of the target material. However, the inherent image motion is maintained in the image display device. This moving image is disconcerting and ultimately causes observer fatigue plus prevents direct study of a particular portion of the image for a reasonable time. The target material exhibits a particular temporal response which can be optimized through correct scan speeds of the infrared image over the target material.